Zero Compression 5 & 6 on fresh rebuild-258 - JeepForum.com
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post #1 of 11 Old 10-03-2016, 08:36 AM Thread Starter
darrendeatz
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Zero Compression 5 & 6 on fresh rebuild-258

I have a theory on the issue, I'd like your input as well. Here are the facts:

Just completed a complete overhaul and rebuild, including new bore and pistons, rings, bearings, gaskets...the whole package. The head was reworked by my machine shop. valves ground, ported, new valve guides and the head was surface machined.

Reassembled using existing head bolts and a new Fel pro 8169PT with no sealers or dressings. Torqued to 85 ft-lbs according to the spec and pattern indicated in the Haynes Repair Manual.

Fired it up. Timing was at TDC, got a pretty loud backfire through the Carb, so I CC rotated the distributor and fired again. Fired right up and the timing was right on. Ran good, sounded good, except that it sounded like it was missing on a cylinder. Turned out to be missing on both 5 and 6.

Checked compression on all six: 1-125, 2-130, 3-125, 4-130, 5-000, 6-000. CRAP!

I pulled off the VC, everything looks good. pushrods, rockers, springs valves...all function fine. Ran a camera down in 5 and 6, all looks good. Pulled off the head, valves seated correctly, absolutely no sign of any problem. Head gasket looks fine. Also, no sign of coolant in the oil. No physical issues observed to explain zero compression. What could it be???

My theory was that 85 ft-lbs is too low for this fel-pro permatorque head gasket and I lost compression between 5 and 6. However, I don't see any visible evidence on the gasket of a breach between 5 and 6. I don't see evidence of anything. It's also possible that my torque wrench was not accurate and perhaps not reaching a true 85 ft-lbs.

Help me out here. What could it be? Should I see evidence of compression loss around the gasket? The engine ran for maybe 20 minutes total. I'm not ready to consider ring failure, because they were new rings and would have to happen in 2 cylinders...unlikely on a fresh build.

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post #2 of 11 Old 10-03-2016, 10:41 AM
Fourtrail
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I would go over the rocker arm/pushrod combination for 5 and 6. it sounds like something might not have seated correctly and you are holding a valve open all of the time. even though your rings haven't fully seated, you should see higher compression numbers. If they decked the head, block and ground the valves, your pushrods could be a touch too long.

80 CJ-5, 74 CJ-6, 56 CJ-5
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post #3 of 11 Old 10-03-2016, 03:33 PM Thread Starter
darrendeatz
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Thank you, kindly, Fourtrail. I will check rocker positions thoroughly when I reassemble. I think I can precisely measure any spring depression after tightening down the rocker arm pivots. I should be able to spin the push rods with the piston at TDC. The machine shop took .015 off the head, didn't touch the block. Told me that .015 shouldn't be enough to cause a problem. Doesn't seem like enough to be a problem, but maybe.
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post #4 of 11 Old 10-04-2016, 03:42 PM
Theman1945
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85ft lbs? Hmm... Everything I've read is 100ft lbs. If what fourtrail says doesn't work, Follow the spiral pattern in the book 3 times: 1 at around 35ftlbs, second time 70ftlbs, and finally 100ftlbs. Also, did you clean the threads and lube the bolts? Even when the block is cleaned by the shop, small bits of debris may be left behind in the threads in the block. I have used a combination of a shotgun bore cleaning bristle and a shop vac to get anything out. With the exception of the bolts which run into water jackets which you need to seal, dip the bolt in old fashioned straight 30w oil just before you put it in. Sometimes when getting to higher torques, the bolts will bind (chances increase with debris) and end up stopping short.

If none of these work, get a new, good quality set of head bolts. Many bolt sets are made to be used once, ie the instructions will say torque to xyz and then turn 1/4 turn. So your bolts might just be a hair too long. I'd go with a high quality set, such as those from ARP.

Hope this helps; keep us updated!

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post #5 of 11 Old 10-05-2016, 09:18 AM Thread Starter
darrendeatz
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Thank you, @Theman1945 for the advice. I blasted the bolt holes with air, but only lightly lubricated the bolts. I threaded each bolt with my fingers for feel. With exception to #11, they all seem to run down easily until head contact.

I followed the Haynes manual pattern, and 3 stepped the bolts to 85. Haynes did not mention the 3 stepping. I was leary about the 85 ft-lbs, but could not find a reliable source suggesting otherwise. My Haynes manual was last revised in 2012, but that doesn't mean the data has been updated to account for new technology such as the PermaTorque gasket I'm using. I still suspect the Torque # to be the problem, but Fourtrail has a good point about the length of the pushrods.

I plan to torque to 105, then closely inspect each valve position with each cylinder at TDC....something I should have done the first time.
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post #6 of 11 Old 10-05-2016, 12:36 PM
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Originally Posted by darrendeatz View Post
Thank you, @Theman1945 for the advice. I blasted the bolt holes with air, but only lightly lubricated the bolts. I threaded each bolt with my fingers for feel. With exception to #11, they all seem to run down easily until head contact.

I followed the Haynes manual pattern, and 3 stepped the bolts to 85. Haynes did not mention the 3 stepping. I was leary about the 85 ft-lbs, but could not find a reliable source suggesting otherwise. My Haynes manual was last revised in 2012, but that doesn't mean the data has been updated to account for new technology such as the PermaTorque gasket I'm using. I still suspect the Torque # to be the problem, but Fourtrail has a good point about the length of the pushrods.

I plan to torque to 105, then closely inspect each valve position with each cylinder at TDC....something I should have done the first time.
No problem, I understand how frustrating having problems with a freshly rebuilt engine can be! After hours of frustration, multiple other mechanics, and two separate leakdown tests, we concluded that Enginetech (or the person selling their product via eBay) shipped the incorrect overbore size piston rings with my kit. So until I take everything apart and replace them, I have a freshly rebuilt engine which goes through a 2qts of oil driving from DFW to Stillwater, OK.

http://www.torkspec.com/torkspecme.a...-4.2L-258ci-S6 I use this website for my "not-critical" torques, however it does say 100ftlbs for the head bolts. In addition, my ARP bolts came with specific instructions to either 100 or 105 ftlbs, I'm not sure which.

When I started out I had both a Haynes and Chiltons. As I read through both I found that much of the information I needed was either missing or generic across all wrangler models. Eventually, after mentioning my use of them to my engine machinist, I was told the only thing they're good for incudes starting fires . I still have them because they do help from time to time, I'm just upset cause I feel as if haynes could've done a much better job.

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post #7 of 11 Old 10-06-2016, 07:18 AM Thread Starter
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Yes, I've not been too impressed with the Haynes Manual. They seem to cover what any amateur should find obvious, such as "reassemble in the reverse order from disassembly".

So, here's what's happened since yesterday. I dropped the head back on and torqued it down. Noticed, as I tightened down the rocker pivots that each rocker was depressing the valve spring between .097 and .130 while that piston was at TDC. Not good. Now, I have zero compression in all 6. Talked to my mechanic. He believes that the lifters swelled up over the last 4 days while there was no pressure holding them back. Now, they are full of oil and need to be bled off. This theory makes sense because the engine did run for about 30 minutes when it was only 5 and 6 with no compression.

Now, I'm trying to figure out how to bleed them off without pulling them out. Mechanic believes they will slowly seep back down to where they are supposed to be, but that could take a very long time. I'm trying to find out of there is a tool, or a method to do this.

1. Does this theory hold water? (or, oil)
2. Any ideas on how to bleed hydraulic lifters in place?
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post #8 of 11 Old 10-10-2016, 12:33 AM
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Quote:
Originally Posted by darrendeatz View Post
Yes, I've not been too impressed with the Haynes Manual. They seem to cover what any amateur should find obvious, such as "reassemble in the reverse order from disassembly".

So, here's what's happened since yesterday. I dropped the head back on and torqued it down. Noticed, as I tightened down the rocker pivots that each rocker was depressing the valve spring between .097 and .130 while that piston was at TDC. Not good. Now, I have zero compression in all 6. Talked to my mechanic. He believes that the lifters swelled up over the last 4 days while there was no pressure holding them back. Now, they are full of oil and need to be bled off. This theory makes sense because the engine did run for about 30 minutes when it was only 5 and 6 with no compression.

Now, I'm trying to figure out how to bleed them off without pulling them out. Mechanic believes they will slowly seep back down to where they are supposed to be, but that could take a very long time. I'm trying to find out of there is a tool, or a method to do this.

1. Does this theory hold water? (or, oil)
2. Any ideas on how to bleed hydraulic lifters in place?
I have no idea how to bleed them in place... You'll probably have to remove the head again and take them out with a magnet, and then remove the oil one by one after they're out.

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post #9 of 11 Old 10-10-2016, 04:44 PM
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They should bleed back down under the pressure of the valve spring trying to close. There is a Ford tool out there that slides over the rocker arm that allows you to use the rocker/pushrod to add pressure and compress the lifter and help accelerate the bleed down time. Search hydraulic lifter bleed down tool or tappet bleed down wrench, but I am not sure if the ones out there will work on the AMC rocker arm configuration. Also at 3.99 each for new sealed power brand lifters from summit, it is probably cheaper to throw a new set of lifters in than to buy the tool to force bleed them down.

80 CJ-5, 74 CJ-6, 56 CJ-5
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post #10 of 11 Old 10-14-2016, 10:59 AM Thread Starter
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So, I let it sit for about 4 days. Cylinders 1,2,3 and 4 all bled down correctly and are now making good compression. 5 & 6 were still at zero (they were the two that I originally had a problem with). I decided that maybe they were not going to bleed down enough to close the valves completely, so I shimmed the rockers .030. Of course, when I pulled the rockers off, the lifters swelled a bit, so now I'm waiting a few days for them to settle back down and see if the .030 shims fix the problem. If I'm doing the math correctly (due to the geometry of the rocker), an .030 shim should have a net change of .045 on the valve.

If this fixes the problem, I may order shorter pushrods and pull out the shims. We'll see what happens. If not, I'll try an .045 shim and try again.
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post #11 of 11 Old 10-15-2016, 08:05 PM Thread Starter
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After adding the .030" shims on intake and exhaust of 5 and 6, then waiting 2 days for the lifters to settle in, I now have compression on all six cylinders and she's purring like a kitten. Thanks to all who commented and provided input.
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4.2 liter , compression , head gasket , torque specifications

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